Introducing rice yield loss caused by weed competition into the SimulArroz model

Abstract

The objective of this work was to model weedy rice (Oryza sativa) and barnyard grass (Echinochloa spp.) competition with flood-irrigated rice, introducing it as a submodule into the SimulArroz model. The competition of both weeds with irrigated rice was modeled using the rectangular hyperbola equation. The “i” and “a” coefficients of the rectangular hyperbola for each of these weeds were obtained from the literature and from field experiments carried out in the state of Rio Grande do Sul, Brazil. In SimulArroz, yield loss was applied to penalize yield in all three technological levels (high, medium, and low) of physiological maturity. For weedy rice, the coefficient values of imean for the high, medium, and low technological levels were 1.04, 1.50, and 3.57 respectively, and, for barnyard grass, 4.70, 10.49, and 15.51 respectively. Coefficient “a” was 100 for weedy rice, and amean values for barnyard grass were 101.63, 104.92, and 96.88 for the high, medium, and low levels, respectively. The yield loss approach was suitable to model the competition of weedy rice and barnyard grass with irrigated rice. The submodule yield loss caused by the competition of weedy rice and barnyard grass with irrigated rice improves the predictive capacity of the SimulArroz model.

Status of weed control in imidazolinone-herbicide resistant rice in Rio Grande do Sul

“…Problems caused by barnyardgrass are also related to the severe interference when one plant/m -2 competing with different management technological levels led to grain yield losses from 5% to 15% (Richter et al, 2019). In addition, the large number of mentions of the presence of this weed may also be due to the number of herbicide resistance cases.…”

Effects of Monochoria vaginalis density on yield losses, economic thresholds, and gross returns in paddy rice (Oryza sativa L.)

“…Richter et al. (2019) reported that in weedy rice, the parameter estimates of I at high, medium, and low technological levels were 1.04, 1.50, and 3.57, respectively. Meanwhile, Stougaard and Xue (2005) reported that differences among seed size classes were less evident at higher wild oat ( Avena fatua ) densities, with parameter estimates of 72.4, 72.0, and 66.0, and I parameter estimates of 1.08, 0.52, and 0.46 for small, bulk, and large seed size classes, respectively.…”

“…A number of experimental studies have examined the interspecific competition between crops and weeds (Hossain et al., 2020; Masum et al., 2019; Richter et al., 2019; Tian et al., 2020), using mathematical models to describe the relationship (Cousens, 1991; Tian et al., 2020). However, models such as the RYL model are based on single weed management practices, and are therefore of limited use (Cousens, 1987).…”

An update of new flood-irrigated rice cultivars in the SimulArroz model

“…Since 2012, rice yields have been stable and these cultivars have been used by around 80% of the farmers in the last two crop seasons -2016/2017 and 2017/2018. In recent years, simulation modelling has been among the most used research techniques in Brazil. Its application in the rice area has focused on: the comparative assessment of different crop models in current and future weather scenarios Castro et al, 2018;Ramirez-Villegas et al, 2018), the evaluation of alternative water management strategies (Heinemann et al, 2002), and the study of yield losses caused by weeds (Richter et al, 2019).…”